1. Field of the Invention
The present invention relates to a method of mounting a conductive ball and a conductive ball mounting apparatus, more particularly, a method of mounting a conductive ball and a conductive ball mounting apparatus, for mounting a conductive ball on a wiring substrate or the like to form a bump electrode.
2. Description of the Related Art
In the prior art, there has been a method of forming a solder ball on a connection pad of a wiring substrate on which a semiconductor chip or the like is to be mounted, and thereby forming a bump electrode. In such a method of mounting a solder ball, firstly, as shown in FIG. 1A, a wiring substrate 100 on which solder balls are to be mounted is prepared. In the wiring substrate 100, connection pads 200 are provided on an upper surface of a substrate 110, and a solder resist 300 in which opening portions 300a are provided on the connection pads 200 is formed. Moreover, a flux 400 is coated on the connection pads 200.
Then, as shown in FIG. 1B, a mask 500 to be used for mounting solder balls is disposed on the wiring substrate 100. The mask 500 has a configuration in which a mesh portion 540 is attached to a periphery of a metal mask portion 520, and in which a frame portion 560 is provided on the outer edge of the mesh portion 540. Moreover, opening portions 500a through which solder balls pass are formed in parts of the mask portion 520, the parts corresponding to the connection pads 200 of the wiring substrate 100.
Next, as shown in FIG. 1B similarly, a large number of solder balls 600 are supplied onto the mask 500 and then swept to move to one end side of the mask 500 by a brush 700. Thereby, as shown in FIG. 1C, the solder balls 600 pass through the opening portions 500a of the mask 500 and are arranged to be bonded to the fluxes 400 on the connection pads 200 of the wiring substrate 100. Thereafter, the mask 500 is moved upward to be removed from the wiring substrate 100.
Otherwise, as shown in FIG. 2, there is another method using an air supply 750 instead of the use of the brush 700. In this method, by blowing air to the solder balls 600 from an air supply 750 to move the solder balls 600 to one end side of the mask 500, the solder balls 600 is arranged on the connection pads 200 of the wiring substrate 100 while causing the solder balls 600 to pass through the opening portions 500a of the mask 500.
As the techniques related to the above-described methods of mounting a solder ball, in Patent Literature 1 (Japanese Patent Application Publication No. 2004-186286), it is set forth that, a print mask is disposed on a silicon substrate having columnar electrodes, then a large number of solder balls are supplied on the print mask, then air is moderately blown to the solder balls while a squeegee is moved, thereby, solder balls pass through the print mask, and are arranged on the columnar electrodes.
Also, in Patent Literature 2 (Japanese Patent Application Publication No. 2006-173195), it is set forth that, a large number of solder balls are supplied on a mask disposed on a wafer, then the solder balls are moved by a filling head provided with a sweep member, to arrange the solder balls in opening portions in the mask, then the solder balls remaining on the mask are swept to the outside of the mask by a removal head provided with a soft squeegee, and are removed consequently.
In the above-described prior arts, the solder balls 600 the number of which is considerably larger than that of the opening portions 500a of the mask 500 are supplied on the mask 500. Accordingly, although some of the solder balls 600 pass through the opening portions 500a of the mask 500, some other solder balls 600 remain around the opening portions 500a of the mask 500 in many cases. Such being the case, it is necessary to move the excess solder balls 600 to one end side of the mask 500, or to remove the excess solder balls 600 from the mask 500.
Without this operation, the excess solder balls 600 remaining on the mask 500 may pass through the opening portions 500a of the mask 500 when the mask 500 is moved upward from the wiring substrate 100 to be separated therefrom, and consequently, multiple solder balls are likely to be mounted on the connection pads 200 of the wiring substrate 100, in some cases.
In the method in which the excess solder balls on the mask are moved by the brush, the brush needs to be moved repeatedly with many times in order to remove all the excess solder balls. Consequently, a long time is required for the operation, and, hence, the manufacturing efficiency is low. Furthermore, solder balls sometimes adhere to the brush, which is likely to complicate the maintenance.
In the method in which the excess solder balls on the mask are moved by using air, the wind pressure needs to be set relatively high in order to efficiently move the solder balls. As a result, solder balls on the mask sometimes fly to the outside of the mask in some cases. By contrast, when the wind pressure is set low enough to prevent solder balls from flying to the outside, it is extremely difficult to move all the excess solder balls.